The natural and technological world around us

The what, why, and who of condensed matter physics research

Inna Vishik

UC Davis

Jan 31, 2017

Outline

• Basic vs applied research

• Why do we do research?

• Condensed matter physics research

• My condensed matter physics research

What is research?

• Creative• Systematic• Increasing shared knowledge

Different types of research

Applied Research

Basic Research

How do I make sure the next Samsung galaxy phone does note explode??

What happened in the first few minutes after the Big Bang?

UniversitiesIndustry

PhysicsEngineeringProduct R&D

Why do we do basic research?

• It’s interesting

• It’s fulfilling

• It satisfies (part of) humans’ desire to understand their world

• It’s profitable (for society)

How does society benefit from basic research?

• Educated workforce who has experience solving difficult, open-ended problems

• Technology transfer

• Unexpected applications which are realized decades in the future

Examples of unexpected applications of physics research

Einstein’s theory of special relativity (1915)how does spacetime curve around massive astronomical bodies?

60-85 years later

Clocks on GPS satellites make corrections relative to observers on earth using Einstein’s theories

Examples of unexpected applications of physics research

Particle accelerators: smash subatomic particles into each other in order to investigate fundamental interactions and structures

25-60 years later

Proton therapy: use energetic beam of protons from particle accelerator to selectively target cancerous tissue

Sometimes the unexpected application of research is more research

Circular particle accelerators emit x-rays—synchrotron light

25-40 years later

Dedicated synchrotrons produce bright x-rays for doing experiments in physics, chemistry, biology, engineering, art….

Yes, art! Archimedes palimpset

And sometimes applied research leads to insights in basic science

Researchers at Bell Labs were using a microwave horn antenna to communicate with satellites (1960s)

They discovered a microwave background permeating outer space—an echo of the Big Bang

Summary: the what and why of research• It’s profitable (estimated return on investment: 30-

700%*)

• Applied research aims for short-term profitability

• Basic research aims to amass important ideas, discoveries, and invention for the next generation’s economic profits

• Important feedback loop between applied and basic research

*https://www.mpg.de/799746/W000_Viewpoint_006-009.pdf

Many types of physics research

Astrophysics

Large

Particle physics

Small

Condensed matter physics

manymany

manymany

manymany

manymanymanymany

many

Condensed matter physics: the physics of many

What happens when ~1023

electrons interact with each other and with ~1023 positively charged nuclei which are arranged in an orderly lattice

It turns out that basically an infinite number of things can happen…

metal

Semiconductor Insulator Insulator in bulk, metal on surface

Magnet (and materials which respond to magnet)

Materials which behave as if electrons inside have fractional charge (fractional quantum hall effect)

Materials which behave as if they contain magnetic north poles without corresponding south poles

Is condensed matter physic basic or applied research?

Applied Research

Basic Research

Understanding how impurities in silicon and other semiconductors could be manipulated to make transistors is crucial to all modern electronic devices

These same semiconductors, when prepared in a special way and cooled down to almost absolute zero can host ‘fractionally charged electrons’

Condensed matter physics is both useful and fundamental

Condensed matter physics is both mundane and fantastical

MundaneHoly guacamole

Why is window glass transparent? Materials that expel their magnetic field when

they are cooled (superconductors), and levitate above magnets (Video source: goo.gl/H6kXSW)

Condensed matter physics is simultaneously small and large

Small constituents

Large magnets

Tabletop experiments

Large facility experiments (e.g. synchrotron)

Condensed matter physics is a science which relies on serendipity

H. Kamerlingh Onnes

Liquid heliumMercury

Re

sist

ance

Temperature

?

Surprise discovery: resistance to flow of electricity suddenly goes to zero (a superconductor)

Physicists want to explainsurprising phenomena

Superconductivity is useful (e.g. MRI machines), but how does it work?

Targeted experiment

Development of microscopic explanation

Isotope effect on superconducting transition temperature (1950)

Bardeen-Cooper-Schrieffer theory: superconductivity caused by electrons interacting with atomic vibrations

When a problem is ‘completely solved’, sometimes we can still get a surprise

Bednorz and MullerNobel prize 1987

Paul Chu

77KBoiling point of L-N2

Mechanism of ‘high-temperature’ superconductivity in copper-oxides still not explained

Targeted experiment

Development of microscopic

explanation

Liquid helium~$15/Liter

Liquid nitrogen~$0.30/Liter

Past ~3 years: make ‘high-temperature’ superconductors by mashing hydrides between diamonds

Highest superconducting Tc: onset>190K!

Drozdov et al.ArXiv: 1412.0460

Metallic hydrogen is predicted to be a room temperature superconductor and it was (allegedly) created for the first time last week

R. P. Dias et al., Science 10.1126/science.aal1579 (2017)

Larger than pressure in center of earth!!

Reminder: superconductivity is not the only fun/useful thing that happens in materials

metal

Semiconductor Insulator

Magnet (and materials which respond to magnet)

Materials which behave as if electrons inside have fractional charge (fractional quantum hall effect)

Materials which behave as if they contain magnetic north poles without corresponding south poles

Insulator in bulk, metal on surface

The diversity of materials’ properties largely originates from electrons

Targeted experiment

Development of microscopic

explanation

Material

Why study electrons in this way?

Material

Electrons ejected (photoemitted) by light still carry information about how they were moving in the material

Superconducting materials:

Cooper pair

measure energy to de-pair superconducting electrons

Topological insulators (insulator in bulk, indestructible metal on surface)

Distinguish between surface and bulk electrons and see how they interact

Condensed matter physics is a team effort

Big question: What happens when ~1023 electrons interact with each other and with ~1023 positively charged nuclei which are arranged in an orderly lattice

Chiang, surface microscopy

Curro, NMR

Fadly, xray photoemission

M. Hamidian, STM

Da Silva Neto, STM and RXS

Liu, nanomagnetism

Taufour, xtal growth

Vishik, UV photoemission

Yu, nanocrystals

Zhu, surface science

Zieve, uniaxial pressure

And theorists too!

Conclusions

• Research is useful and profitable, often in ways that are unpredictable at the time the research is done

• Condensed matter physics studies many-particle systems in which a multitude of emergence phenomena appear

• Amazing achievements and discoveries are made daily in condensed matter physics

• Condensed matter physics is a team enterprise, in which different research groups have autonomy over a small subset of the big problems we work on